Why XSS Remains a Critical Threat

Despite being well-understood for over two decades, XSS consistently ranks in the OWASP Top 10 web application security risks. Several factors contribute to its persistence: the increasing complexity of web applications, the widespread use of user-generated content, the challenges of properly encoding output in all contexts, and the devastating impact successful attacks can have. Modern web applications are incredibly complex, often combining server-side rendering, client-side frameworks, third-party libraries, and user-generated content from multiple sources. Each of these components introduces potential XSS vectors if not handled correctly.

The impact of XSS attacks extends far beyond simple annoyances. Attackers can steal authentication credentials, hijack user sessions, deface websites, distribute malware, perform unauthorized actions on behalf of users, and even launch more sophisticated attacks against internal networks. In 2018, British Airways suffered a sophisticated XSS attack where hackers injected malicious scripts into their payment page, stealing credit card details from approximately 380,000 customers. The attack went undetected for over two weeks, demonstrating how stealthy and damaging XSS can be.